M 5.9 - 149 km W of Gold Beach, Oregon

Tectonic Summary

Two earthquakes of magnitude 5.9 occurred off the coast of southern Oregon on June 4th, 2021. The earthquakes struck 25 minutes apart from each other at 07:52 (UTC) and 08:17 (UTC) and were located around 12 km from each other. These earthquakes occurred as the result of shallow strike-slip faulting within a deformed section of the southernmost oceanic crust of the Juan de Fuca plate, commonly called the Gorda plate, west of the Cascadia subduction zone. Focal mechanism solutions indicate that rupture occurred on either a left-lateral northeast-southwest-striking fault or on a right-lateral southeast-northwest-striking fault. Near the location of the earthquakes, the Juan de Fuca plate moves to the northeast relative to the North America plate at a velocity of about 30 mm/yr.

Earthquakes are common in the Gorda plate, which is subjected to internal deformation originating from interactions with both the Pacific plate to the south and the North American plate to the east. The eastern edge of the Gorda plate subducts northeastward beneath the North American plate, while the southern edge forms a transform boundary with the Pacific plate west of the Mendecino Triple Juction. The western edge of the Gorda plate is a divergent boundary with the Pacific plate. Thirteen earthquakes magnitude 6 and larger have occurred within 200 km of these recent earthquakes in the last 50 years. The largest of which was a M7.2 earthquake on June 15th, 2005 that struck about 100 km to the south of the June 4th, 2021 earthquakes.